Add EE usage ping

This MR implements the EE usage ping as a sidekiq-cron async task as discussed in #380. Currently we report:

* Active user count
* Max historical active user count
* License data (e.g. licensee, add-ons, etc.)

Screenshot:

![image](/uploads/552f5445c0034b604c35c2783161cbc1/image.png)


See merge request !557